1. Field of the Invention
The present invention relates to a display apparatus for use with a computer system, and more particularly to a computer monitor for supplying a power supply voltage from an internal power supply therein to computer peripherals via universal serial bus USB hubs.
2. Description of the Related Art
A personal computer serving as a host may have an associated monitor serving as a display apparatus, a keyboard and a printer, a light pen or a plotter. The monitor is connected to the computer via a video cable and the computer provides video signals and the overall information required to control the monitor through the video cable along with information indicative of the monitor processed results from the monitor.
In addition to the keyboard and the monitor, if other peripheral devices, such as a printer, a light pen, a plotter or the like, are connected to the computer, it is complicated to connect the computer to the peripheral devices. Also, since the computer is not provided with a plug and play function, it is difficult for a user to connect the peripheral devices to the computer. To solve the above described problems, a universal serial bus (USB) system has been developed.
A monitor circuit not having a USB system has five main sections, a power supply, a video signal processor, a horizontal/vertical synchronization signal processor, a monitor controller and a CRT (cathode ray tube).
The monitor may also have an audio unit for generating an audio signal and a voice input unit for converting an audio signal into an electrical signal.
Such a monitor has the above described problem such as the difficulty of use for PC peripheral expansion and the like. Also, the monitor does not have connectors for communicating with the peripheral devices, such that plug and play functions can not be performed.
In order to solve the above described problem, an earlier invention by the same inventor as that of the present invention adds a hub system used for expansion of computer peripherals. The hub system incorporated into the computer monitor comprises three main sections, a USB system controller, a power switch and a plurality of input/output ports.
The controlling operation is performed in the USB controller. The USB controller receives and analyzes a power control signal from the computer system and the control provides a power switching control signal to the power switch which is composed of a multiplexer circuit and a microcomputer. The power switch designates corresponding ports of the downstream ports in response to the power switching control signal so that power from the power supply can be supplied through the designated ports. The USB controller checks whether the voltage at the designated port is above the limit value of voltage and if so, the control provides an abnormal voltage indicating signal to the computer system and the computer system receives the abnormal voltage indicating signal and generates a cut-off control signal. The cut-off control signal is provided to the computer monitor so that power supply through the designated downstream ports of the monitor is cut off.
In the above described computer monitor; when the power supply voltage is cutoff and the power supply of the monitor, during the power-off of the monitor during the power saving mode, a power supply voltage provided from the power supply or the hub port connected to the host is not supplied to the USB devices which are respectively connected through the hub ports connected to the USB controller. Thus, the USB devices are not operated.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited computer monitor for supplying a power supply voltage from an internal power supply to computer peripherals via a universal serial bus hub as in the present invention: U.S. Pat. No. 5,606,704 to Pierce et al., entitled Active Power Down For PC Card I/O Applications, U.S. Pat. No. 5,640,573 to Gephardt et al, entitled Power Management Message Bus For Integrated Processor, U.S. Pat. No. 5,603,040 to Frager et al, entitled Power Management Control Unit For A Computer Peripheral, U.S. Pat. No. 5,586,333 to Choi et al., entitled Method And Control Apparatus For Generating Power Management Signal Of Computer Peripheral Equipment In A Computer System, U.S. Pat. No. 5,560,022 to Dunstan et al., entitled Power Management Coordinator System And Interface, U.S. Pat. No. 5,522,081 to Carls, entitled Drive Current Detection And Optimization Circuit For Computer Systems, U.S. Pat. No. 5,514,859 to Seigel, entitled Power And Data Interface For Peripheral Devices, U.S. Pat. No. 5,483,656 to Oprescu et al., entitled System For Managing Power Consumption Of Devices Coupled To A Common Bus, and U.S. Pat. No. 5,475,271 to Shibasaki et al., entitled Power Source Control System For Electronic Device And Expansion Unit Connected Thereto.